Free Syrian Army fighters look through a hole in a wall in Deir al-Zor on Wednesday.

Photo: Reuters

UN Secretary-General Ban Ki-moon yesterday said his investigating team would report back this week on the suspected use of chemical weapons in Syria as embattled Syrian President Bashar al-Assad vowed to resist any US strike.

US President Barack Obama said on Wednesday he has yet to make a decision on hitting Syria over horrific attacks last week that activists say killed hundreds of people and threatened to draw the West into the brutal 29-month conflict.

A Western bombing blitz had appeared imminent earlier this week, but US allies were increasingly reluctant to act before hearing the results of a UN chemical weapons probe.

Ban said the UN experts — on a third day of inspections of alleged attack sites near Damascus — would leave Syria by Saturday and report to him immediately.

He appealed to divided international powers to work together to head off military action against Syria, where the UN says 100,000 people have been killed and several million made homeless since the conflict erupted in March 2011.

“Diplomacy should be given a chance ... peace ([should] be given a chance,” Ban said.

With any US-led missile strike unlikely to have UN Security Council backing, key Damascus allies Russia and Iran again warned against any Western intervention, saying it could set off a wider regional conflict.

“Syria will defend itself in the face of any aggression,” al-Assad said, adding that any attack would result in “victory” for the Syrian people.

On the ground, soldiers were being pulled back from their command posts and tougher security controls were in place at roadblocks and hospitals in case of possible air strikes.

Syria’s nervous neighbors have also stepped up preparations for conflict, with Israel authorizing a partial call-up of arm reservists, while Turkey put its forces on heightened vigilance.

Britain, whose government faced a parliamentary revolt, insisted any military action would be allowed under international law as “humanitarian intervention.”

Russia was reportedly sending warships to the Mediterranean, while Britain said it was sending fighter jets to Cyprus.

International pressure for action mounted after grisly pictures emerged after the Aug. 21 attacks in Ghouta, east of Damascus, showing dead children who appeared to have been gassed to death. Damascus denied it deployed chemical weapons and blamed the attack on rebels.

Obama, who a year ago warned that the use of chemical weapons in Syria would cross a “red line,” said on Wednesday that Washington had definitively concluded that the al-Assad regime was to blame.

Asked how close he was to ordering a US strike, Obama told PBS NewsHour: “I have not made a decision.”

He said US action would be designed to send a “shot across the bow” to convince Syria it had “better not do it again.”

Senior US lawmakers are expected to be briefed yesterday about classified intelligence on the chemical attack.

The UN team had arrived in Syria last week to probe allegations of previous chemical attacks, including one in March in Khan al-Assal, near the northern battleground of Aleppo.

Washington had bluntly signaled that a UN Security Council resolution that could have given a legal basis for an assault was going nowhere owing to Russian opposition.

In London, lawmakers were set to vote on a response to the attacks, but British Prime Minister David Cameron was forced by a parliamentary revolt to pledge he would not order military action before the UN inspectors’ report was published.